PARK CITY, Utah -- The filmmaker behind the new documentary about the Penn State sexual-abuse scandal says that both the family of Joe Paterno and the lawyer for the victims expressed satisfaction with the film.

"To have total polar opposite perspectives feel a sense of gratification that the film represents their perspective accurately is really something I am proud of," said documentarian Amir Bar-Lev in an interview at the Sundance Film Festival, where his documentary "Happy Valley" premiered. Bar-Lev screened the film for Joe Paterno's widow, Sue, his two sons, Scott and Jay, and attorney Tom Kline before it premiered at Sundance. All appear in the film.

"Happy Valley" explores the case that engulfed the town of State College, Penn., where Penn State is based and which is also known as Happy Valley. Jerry Sandusky, the former Penn State assistant football coach, was accused of molesting children, and key people, including former head coach Paterno, were said to have turned a blind eye.

Paterno died with a tarnished image and the town was rocked by their fallen saints. Jerry Sandusky did not speak for the movie, but his son Matt Sandusky did.

To get Matt Sandusky to agree to participate in the documentary about his father, Bar-Lev assured him the movie wouldn't solely rely on the stories of Sandusky or Paterno. Instead, it would focus on the torn Happy Valley community.

"Matt asked me a lot of questions about my approach," said Bar-Lev. "Convincing him was really about sitting down with him and telling him that this film was called 'Happy Valley,' not Sandusky or Paterno. It was from that meeting that he said yes and agreed to an interview with no stipulations."

On Sunday, Matt Sandusky attended the premiere of "Happy Valley."

"I felt it was important to share my perspective as a survivor in this documentary," Matt Sandusky told The Associated Press in an emailed statement. "After seeing the film, I am hopeful that it will help people understand some of what I have gone through. Now, I am moving forward as an advocate, forming a foundation dedicated to empowering survivors and educating communities about child sexual abuse."

Matt Sandusky was listed as a defence witness at his father's 2012 trial, but he did not take the stand. Instead, he disclosed through lawyers that he had also been abused. Though Jerry Sandusky, who is serving a 30- to 60-year prison term, was convicted on 45 counts involving 10 boys, he maintains his innocence and is appealing his conviction.

In the film, Matt Sandusky expounds on his upbringing, the abuse he endured, and his tarnished relationship with the Sandusky family after he revealed he'd been abused by his father. He says Sandusky did, in fact, do great things for him, "but there's another part that destroys you," he added.

Matt Sandusky is one of six children adopted by Jerry and Dottie Sandusky. He filed a motion last year to have his name, and that of his wife and four children, legally changed. The court filing outlining the change has been sealed.

In letters released by Judge John Cleland in October 2012, Dottie Sandusky cast a critical eye on Matt Sandusky's claims. She wrote that he had been diagnosed with bipolar disorder, but that he refused to take his medication and that he "had many run-ins with the law."

"I suppose that anybody in the film could be shining me on," said Bar-Lev, who also directed "The Tillman Story." "But I think Matt's believability and candour speak for themselves. Matt is not the only one who has been called untrustworthy, but his story matches many of the other stories. If you think that he is making this up, then you have to believe that the 25 other people also made it up."

No other members of the Sandusky family agreed to participate in this film. However, attorney Kline and members of the Paterno family gave on-camera interviews, including Sue Paterno, who had fond memories of the family environment that existed at Penn State during her late husband's life. "It was good we all had that time," she said.

Footage shot last Thanksgiving shows a happy Matt Sandusky with his four kids at home in Pennsylvania. "So much of the movie is an explanation of a moral puzzle that doesn't have easy answers," said Bar-Lev. "But Matt's attention to his family and his enjoyment of his family was one kind of answer to the puzzle."